Cornwall Fire and Rescue received 12 hoax calls on Sunday, the service has said.
Critical Control Centre operators realised they were bogus calls and no crews were sent out.
A Cornwall Fire and Rescue spokesperson said: “A hoax call to any Emergency Service could cost lives; tying up valuable emergency resources and preventing them from attending a real incident.
“If there had been a genuine emergency, resources would have to be called in from another station further away. Putting lives at risk.
“Making hoax calls is illegal. People can, and have been, heavily prosecuted for making hoax calls with a fine of up to £5,000 or six months in prison.”